The present invention is directed to ink compositions, and more specifically, the present invention relates to inks with an ink melting point of, for example, between about 60.degree. C. and about 150.degree. C., and preferably between about 70.degree. C. to about 90.degree. C., and which inks are especially useful for acoustic ink printing, processes and apparatuses, reference, for example, U.S. Pat. No. 5,121,141, U.S. Pat. No. 5,111,220, U.S. Pat. No. 5,128,726, U.S. Pat. No. 5,371,531, the disclosures of which are totally incorporated herein by reference, including especially acoustic ink processes as illustrated in the above recited copending applications, such as an acoustic ink printer for printing images on a record medium.
The inks of the present invention in embodiments can be considered phase change inks, that is, for example, an ink that changes from a liquid state to solid state in a suitable period of time, for example, from about 1 to about 100 milliseconds and preferably in less than about 10, such as from about 2 to about 7 milliseconds, and which inks are comprised of: (1) a phase-change color spreading compound, or an additive that preferably fills the pores of a substrate, such as paper, and which compound has a melting point of, for example, lower than about 120.degree. C. and preferably between about 60.degree. C. to about 100.degree. C., and with a low acoustic loss value of below about 100 dB/mm, (2) a non-aqueous diluent additive with, for example, a boiling point higher than about 150.degree. C., and more specifically, with a boiling point of from about 150.degree. C. to about 225.degree. C. and preferably from about 170.degree. C. to about 200.degree. C., and a melting point of less than about 60.degree. C., and with a low acoustic loss, which enables a reduction, or minimization of energy consumption, and which acoustic loss is preferably in the range of from about 5 to about 60 dB/mm, and preferably between about 5 to about 40 dB/mm, (3) a lightfast UV absorber, (4) a lightfast antioxidant, (5) and a colorant such as a dye, a pigment or mixtures thereof. More specifically, the present invention is directed to phase-change acoustic ink compositions comprised of: (1) a nonaqueous thiourea, or an oxime compound vehicle with, for example, a melting point of lower than about 120.degree. C. and preferably between about 60.degree. C. and about 100.degree. C., and preferably with a low acoustic loss and which acoustic loss is, for example, below about 100 dB/mm, and preferably in the range of between about 25 to about 80 dB/mm at the jetting temperature, (2) a nonaqueous diluent derived from a carbamate, thiourea, or an oxime compound, each with a boiling point of higher than about 150.degree. C. and lower than about 350.degree. C., and preferably between about 170.degree. C. to about 300.degree. C., and a melting point of less than about 60.degree. C. and with low acoustic loss and which acoustic loss is below about 60 dB/mm, and preferably in the range of from about 35 to about 55 dB/mm, (3) a UV absorber, (4) an antioxidant, and (5) a colorant, and wherein there can be generated with such inks excellent developed images on plain and coated papers with acceptable image permanence, excellent projection efficiency on transparencies without a post fusing step, and excellent crease resistance, and wherein the inks possess acceptable, and in embodiments superior lightfastness of, for example, between about 90 to about 100 percent, and superior waterfast values of, for example, between about 95 to about 100 percent. Moreover, in embodiments of the present invention there is enabled the elimination, or minimization of undesirable paper curl since water need not be present, or minimum amounts less than about 1 percent of water may be selected in embodiments in the invention inks, and it is preferred that there be an absence of water. When water is not present in the inks a dryer can be avoided thereby minimizing the cost of the acoustic ink jet apparatus and process.